Journal of Astronomy in Culture

The orientation pattern of the apses of 98 colonial Catholic churches in the Philippine archipelago (16th–19th centuries) and three in Guam (Mariana Islands, 17th century) has been studied and found not to follow the canonical eastward alignment toward sunrise, except perhaps in churches built during the 16th century. This suggests that pre-Council of Trent temple building traditions appear to have been preserved in some form initially, but were largely abandoned from the 17th century onwards. No relationship has been identified between orientation and religious factors such as founding orders or dedications, nor have consistent patterns been observed across most islands. Instead, geographical and environmental factors appear to have influenced church layout, this is more clear in Luzon. Naves were generally oriented to avoid the northeast–southeast monsoon axis; inland churches followed local valleys and rivers, while coastal churches were typically arranged perpendicular to the shoreline, with facades facing the sea to improve ventilation in accordance with Spanish colonial planning rules. Possible solar alignments related to feast days were explored, and although not statistically significant, several notable cases were identified for further study.